1. Field of the Invention
The present invention is directed to an adaptive stepper for use in conjunction with a weld controller to control the amount of heat boost which is supplied to the electrodes of a welder.
2. Description of the Prior Art
Weld controllers in the prior art employ a manual stepper to adjust heat boost, typically, as a series of linear step profiles specified by a weld engineer. More particularly, a conventional or manual stepper increases or decreases the heat boost in one percent increments as a function of the number of welds made with a set of electrodes. By way of contrast, the invented adaptive stepper decreases heat boost as a function of expulsions and the current heat boost, and increases heat boost as a function of welds made, the current heat boost and expulsions. That is, the invented adaptive stepper differs from a conventional stepper in that heat boost is determined by the weld controller as a function of expulsion, welds made and the current heat boost, rather than by a series of linear step profiles specified by a weld engineer.
U.S. Pat. No. 4,446,810 teaches an adaptive schedule weld controller system wherein welding current is reduced if the time rate resistance change between the welding electrodes exceeds a maximum predetermined value and increases the welding current if the resistance change is less than a minimum predetermined value. Additionally, the weld current may be turned off when a decrease in resistance from a peak resistance value has reached a predetermined percentage of the peak resistance value, or after a predetermined number of current cycles have been completed. However, while the method taught by U.S. Pat. No. 4,456,810 varies the weld current as a function of computed resistance at the electrodes, and can terminate the weld current as a function of the number of welds made, it differs from the present invention in that the method taught in the patent does not take into account the history of the electrodes when increasing or decreasing heat boost. For example, unlike the present invention, the patent does not include the current heat boost or the welds made count for the electrodes.